The present invention relates to an aircraft wing structure profiled suspension pylon.
It is known that certain aircraft comprise profiled pylons suspended from their wing structure and projecting from the pressure face thereof. Such pylons are intended for suspending devices such as engines, weaponry, fuel tanks, etc., under the wing structure.
Naturally, these pylons and the devices suspended from them give rise to disturbances in the aerodynamic flow over the wing structure and this locally results in a loss of lift and an increase in drag. These unfavorable aerodynamic effects are moreover worsened because, for structural reasons in particular, said pylons are, on the one hand, relatively wide and, on the other hand, have their trailing edge in the vicinity of the trailing edge of the wing structure, such trailing-edge proximity increasing the risks of airstream detachment.
To overcome these drawbacks, the airbus A320 has, from as early as 1986, been using a fairing for reducing the local loss in aerodynamic lift due to such a suspension pylon; this fairing (which is described, for example, in EP-A-0 432 972) being arranged in contact with the pressure face of said wing structure and extending, on the one hand, heightwise, over part of said pylon and, on the other hand, toward the rear of the wing, as a continuation beyond the trailing edge thereof. A known fairing such as this has the approximate shape of a right parallelepiped ending at the rear in a rounded-vertex pyramid. The upper surface of the fairing, projecting beyond the trailing edge of the wing structure, continues the suction face thereof and the width of the said fairing corresponds to the maximum width of said pylon, which means that the lateral faces of said fairing extend the maximum-width section of said pylon rearward.
For a medium-sized airplane, this known fairing is of acceptable dimensions. However, for a large-sized airplane it is necessarily lengthy and bulky, which gives rise to heavy aerodynamic loadings exerted on said fairing in flight. This entails stiffening it, which results in a penalizing increase in mass.
Furthermore, when the wing structure has mobile trailing-edge elements, such as wing flaps, this fairing has itself to be mobile. In this case, for certain flight configurations, the fairing may find itself at least partially in the hot air jet from an engine (the temperature of which may be as high as 700xc2x0 C.), which means that it then has to be made of heat-resistant materials and designed to withstand these high temperatures. This then results in mass constraints and additional production costs.
The object of the present invention is to overcome these drawbacks.
To this end, according to the invention, the aircraft wing structure suspension pylon, said wing structure comprising a pressure face, the rear part of which is concave and set back with respect to its front part and said pylon:
being suspended from said wing structure, projecting with respect to said pressure face of the wing structure and being profiled to comprise, between its leading edge and its trailing edge, a section of maximum width; and
being equipped with a fairing for reducing the local loss of aerodynamic lift, which:
is placed in contact with the pressure face of said wing structure and extends heightwise over part of said pylon;
extends toward the rear of the wing structure, with lateral faces in aerodynamic continuation of the maximum-width section of said pylon; and
extends toward the rear of the wing structure, beyond the trailing edge thereof, in the form of a projecting rear part with an upper surface in aerodynamic continuation of the suction face of said wing structure,
is noteworthy in that:
said maximum-width section of said pylon is arranged at the front of said concave and set-back rear part of the pressure face of the wing structure; and
said fairing for reducing the local loss in aerodynamic lift:
is housed, at least over most of its height, in the concavity of said rear part of the pressure face of the wing structure, and
comprises an underside which comes close to said upper surface, in aerodynamic continuation of the suction face of the wing structure so as to give said projecting part of said fairing the shape of a blade which tapers toward the rear and ends in an aerodynamic trailing edge.
Thus, by virtue of the present invention, a flat small-sized fairing is obtained which is able to solve the abovementioned problems of the known fairing. It will be noted that the aerodynamic trailing edge of said faring makes it possible to considerably reduce the length of the part thereof which projects beyond the trailing edge of the wing structure for aerodynamic efficiency of the same order. Experience has shown that the present invention makes it possible to reduce the height of the fairing by about 80% and to reduce the length of said projecting part thereof by about 50%, with respect to this known fairing, for essentially equal aerodynamic efficiency with respect to the risk of airstream detachment at the trailing edge of the pylon and with respect to loss-of-lift problems. Such a reduction in the dimensions therefore makes it possible to avoid the mass and bulkiness drawbacks mentioned hereinabove and, in the case of a mobile fairing near to the hot jet from an engine, makes it possible to reduce the constraints on the design and the kinds of material to use.
In order to further improve the limitation on the thickness of the fairing according to the present invention, it is advantageous for its underside to be concave.
As regards the trailing edge of the rear part of the fairing, the present invention envisages a number of embodiments. For example:
the lateral faces of the projecting rear part of the fairing may, just like those of that part of the fairing facing the pressure face, be at least approximately parallel to one another, in the continuation of the maximum-width section of the pylon. In this case, the trailing edge of the fairing is elongate, for example rectilinear, and may be at least roughly parallel to the local trailing edge of the wing structure;
or alternatively, as an alternative variation, the lateral faces of the projecting rear part of the fairing may, unlike those of the part of the fairing facing the pressure face, converge toward each other in the direction of the rear. In this case, said lateral faces may be convex and may define, for said fairing, either a relatively elongate, for example rectilinear, trailing edge, or a trailing edge which is at least essentially localized to a point.
Whatever the embodiment of the trailing edge of the fairing, it goes without saying that it is necessary to make sure that the shape of the projecting rear part thereof does not give rise to airstream detachments which would increase drag.
Furthermore, in order to avoid the projecting rear part of the fairing according to the present invention being submerged in the viscous effects of the boundary layer in the vicinity of the trailing edge of the wing structure (which would appreciably reduce the aerodynamic efficiency of said fairing), it is important that, at said trailing edge of the wing structure, the thickness of said fairing be greater than the thickness of the boundary layer of the aerodynamic flow over said wing structure.